A recent late season cold snap with accompanying freezing rain and snow has Ohio corn growers questioning the fate of their newly planted crop. But Ohio State University agronomists say the crop is tougher than most would believe it to be.

“In regards to the freezing event, I think that the chances for recovery for corn are pretty good,” said Ohio State University Extension agronomist Peter Thomison. “The lethal effects of freezing temperatures are usually not a major issue for us. We’ve had similar conditions in past years and came out of those problems with little damage and pretty good yields.”

Warm, dry weather the past several weeks has driven corn producers to the fields. With over 70 percent of the corn already planted in many areas and the remainder half-planted, it could very well be the earliest that the corn crop has been established.

Agronomists generally downplay the impact of low-temperature injury in corn because the growing point is at or below the soil surface, thereby protecting it from air temperatures. Additionally, the plant’s cell contents can act as an “antifreeze,” protecting plant tissue from temperatures as low as 32 degrees Fahrenheit.

“Probably a greater concern to us is how long soils remain saturated,” said Thomison. “If we get periods of cloudy conditions that prevent drying out and the soil remains saturated, then we are probably opening the doors to seedling blight problems.”

Said Pat Lipps, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, “Cold temperature injury can play a significant role in predisposing plants to root infection and blight. Under normal conditions plants can continue to grow and produce new roots, but when other injuries occur, new roots cannot develop rapidly and Pythium and other soil fungi can kill stressed plants.”

Additionally, excessive rainy weather can cause problems to already damaged corn, said Lipps.

“Bacterial soft rots can destroy the corn growing point,” he said. “If growing conditions are favorable, the plants typically outgrow bacterial damage. But if weather remains cold, wet and cloudy following the freezing event, the potential for bacterial damage increases.”

Freeze-damaged corn plants may also suffer cosmetically from a twisted whorl condition. Thomison said that the freezing conditions prevent the leaf from unfurling normally, resulting in a tied leaf whorl.

“The damage resembles the tight leaf rolling often associated with herbicide injury,” said Thomison. “But the plants tend to outgrow this condition when growing conditions improve.”

Though it’s too early to tell what damage, if any, has been caused from the cold temperatures, growers can evaluate the seedlings or the newly germinated plants to determine the extent of any damage. Thomison said that mushy seedlings or rotting growing points are a sign of potential seedling blight problems. The solution to such a situation is to replant.

The unusual weather that could give growers problems with their crop was the result of storms that blew through Ohio over the weekend, dumping as much as a foot of snow in some areas and producing freezing rain and freezing temperatures throughout the state.

Ohio corn growers begin planting in April, sooner or later, depending on the weather.

“Growers have to plant when the growing conditions are favorable,” said Thomison. “Long-term historical data in Ohio shows that during the optimal planting time there is about one day out of three when field work can occur, and this varies depending on soil drainage. Because it’s so wet during this time of year, growers took advantage of the favorable conditions to plant and now they may have to wait a couple of weeks to find out how the plants have responded to these most recent weather conditions.”

For latest updates on crop conditions, log on to Ohio State University’s Agronomic Crops Team Crop Observation and Recommendation Network (C.O.R.N.) newsletter at http://corn.osu.edu.

Manhattan, Kansas
April 26, 2005

Freezing temperatures may have nipped newly-emerged corn

Late April temperatures that dipped below freezing may have burned or even killed leaves on newly-emerged corn in some parts of Kansas, but Kansas State University agronomist Dale Fjell said it's unlikely that yields were compromised – this time.

"The plant itself should survive and develop new leaves," said Fjell, who is the agronomy state leader with K-State Research and Extension. "The growing point of corn plants should still be below the soil, so that provided some protection."

The growing point on a corn plant typically doesn't emerge from the ground until the plant has six leaves. Most corn in Kansas was not that far along, he said.

Numerous weather stations around the state recorded low temperatures in the upper 20s the morning of April 24, according to State of Kansas climatologist Mary Knapp. Temperatures at Goodland fell to 29 degrees, while Hays dipped to 27, Hill City to 28 and Hutchinson came in at 26 F. Readings at the Manhattan airport fell to a low of 24 degrees, and Lawrence posted a 26-degree low.

"Most of the low temperatures were at or just before sunrise, and it warmed up very quickly once the sun came up," Knapp said. "That may have minimized damage to crops."

For example, Hays was at 30 degrees at 4 a.m., 27 at 5 a.m., 30 at 6 a.m. and 36 by 7 a.m., Knapp said. The trend in other locations was similar.

While the late April freeze probably did not kill corn plants, it may slow development and could delay tasseling, Fjell said.

A corn plant typically has 19 to 21 leaves at maturity. Those early leaves usually serve their function – to help the early development of the plant – and then drop off anyway, he said.

"For the most part, corn likely got through this cold snap unscathed," the agronomist said. "Now if we have a freeze or hail damage later on after the growing point has emerged from the ground, then we could have a problem."

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus in Manhattan.